I have never heard of it before. My Medical Dictionary says its
swelling of the glands, lymph nodes. I have known people who
had trouble and/or ran into physical problems after having
a flu shot. One person I know, lost use of the limb in which
the shot was given. But I don't know why that happened. I understand your reasoning for getting the flu shot, to protect
your dad. And I'm sorry you ran into difficulty. Prayers for your daddy!